Goal:
  
  A : Type
  i : positive
  x : A
  IHi : forall (m : tree' A) (j : positive),
        i <> j -> get' i (set' j x m) = get' i m
  a : A
  j : positive
  H : xO i <> xO j
  ============================
   (get' i (set0 j x) = None)


DEBUG:Going to execute:
apply gso0; congruence
DEBUG LTAC Evaluated term: IHi
Level 0: Backtrace:

In environment
A : Type
i : positive
x : A
IHi : forall (m : tree' A) (j : positive),
      i <> j -> get' i (set' j x m) = get' i m
a : A
j : positive
H : xO i <> xO j
Unable to unify "get' i (set' ?M1924 x ?M1923) = get' i ?M1923" with
 "get' i (set0 j x) = None".
Level 0: Backtrace:

In environment
A : Type
i : positive
x : A
IHi : forall (m : tree' A) (j : positive),
      i <> j -> get' i (set' j x m) = get' i m
a : A
j : positive
H : xO i <> xO j
Unable to unify "get' i (set' ?M1924 x ?M1923) = get' i ?M1923" with
 "get' i (set0 j x) = None".